This invention relates to a hydraulic torque impulse generator primarily intended for a screw joint tightening power tool. In particular the invention concerns a hydraulic torque impulse generator, comprising a drive member connected to a rotation motor and including a cylindrical fluid chamber partly defined by a circumferential wall, an output spindle rotatably supported in coaxial relationship with said drive member and having a rear portion extending into said fluid chamber, said rear spindle portion having two radial slots each supporting a radially movable seal element for sealing cooperation with seal lands on the fluid chamber wall, and first seal ridges on said rear spindle portion for sealing cooperation with second seal ridges on said fluid chamber wall, thereby dividing said fluid chamber into two high pressure compartments and two low pressure compartments during short intervals of the relative rotation between said drive member and said output spindle.
The object of the invention is to accomplish a compact torque impulse generator of the above type in which there is generated just one torque impulse during each full revolution of the drive member relative to the output spindle, and in which the frictional wear of the seal elements is brought down to a minimum.